US2342790A

US2342790A - Control system

Info

Publication number: US2342790A
Application number: US435695A
Authority: US
Inventors: Willard G Cook
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1942-03-21
Filing date: 1942-03-21
Publication date: 1944-02-29
Anticipated expiration: 1961-02-28

Description

Feb. 39, 1944. w. a. COOK 2,342,790

CONTROL SYSTEM Filed larch 21, 1942 WITNE SSES: mvENrok Vl i/lara 6 Cook.

- material is being Patented Feb. 29, 1944 CONTROL SYSTEM Willard G. Cook, Wilkinsburg, Pa.,

Electric & Manufacturing Company, East Pittsburgh, Pa.,

vania Westinghouse Pennsyl assignor to a corporation of Application March 21, 1942, Serial No. 435,695

9 Claims.

My invention relates. generally, to control systems and, more particularly, to a system for controlling the operation 01 electric motors employed to drive a reel for winding up strip material such as cold rolled strip steel, as it is delivered from a roll stand or other work device.

As is well known to the art, reel-motors for strip mills, particularly cold mills, must have a speed range of 2 to 1 and at .times 3 to 1 to vary the reel speed. due to the variation in the mill delivery speed. This is in addition to approximately a 3 to 1 speed range to take care of the coil build-up upon the reel, which is best controlled by varying the field excitation of the reelmotor.

The speed variation of the reel-motor, which is to take care of thevarlatlon in-the mill delivery speed, is usually obtained by varying the voltage applied to the reel-motor armature. However, it

cold rolling mills speeds when heavy material is being rolled with greater than normal tensions being required, and at high speeds when light rolled with corresponding lower tension requirements. When it is considered that as much as 1000 horsepower reel-motor capacity may be required to handle the reel under all operating conditions it is apparent that a single large motor would not be satisfactory. Such a motor would be unreasonably large and expensive for the application. In addition, the inertia of the motor would be so large as to make it diiilcult to control during periods of acceleration and deceleration.

In attempting to overcome the dimculties of using a single large motor, two or more separate and relatively small motors have been used. However, in all such instances each motor has been independently controlled and no attempt has been made to provide a common control system for the motors for the purpose ofutilizing them to the greatest advantage.

It is, therefore, the object of my invention, generally stated, toovercome the disadvantages of a single reel-motor of sufllcient capacity to handle heavy material as well as light material and the use of a separate control for each of a plurality of motors; and to increase the capacity of present installations, by providing a control system for a plurality of reel-motors connected in driving relation to the reel which may be utilized to effectively control one or all of the motors.

It is also an object of my invention to provide a Control system for a plurality of reel-motors connected to a reel which will permit the use of one or more of the motors for driving the reel and which will enable the speed of said motors to be simultaneously and automatically regulated directly with that or the mill driving motor.

Another object 0! my invention is to provide a control system of the character described wherein an auxiliary generator and a circuit controlling device are utilized for selectively connecting and operating either one or all of the motors from the main generator.

A further object of my invention is to provide a. control system for a. plurality of reel-motors embodying an auxiliary generator selectively connected in series with the motor armatures and means for simultaneously varying the excitationof the auxiliary generator and the main mill motor so as to. simultaneously vary the speed of the mill and reel.

Other objects. of my invention will either be pointed out specifically in the course of the following description of one form of system embodying my invention, or will be apparent from such description.

Referring to the accompanying single diagrammatic figure of the drawing, there is shown a control system for the motors of a reel ill of a strip rolling mill including a work device or mill stand l2 driven by amotor l4, hereinafter referred to as the mill motor, which receives power from a main generator IS. The reel I0 is driven by 'motors l8 and 20, the armatures of which may be selectively connected ,in series with an auxiliary or booster generator 22 by means of a circuit controlling device 24. A field energization controlling device 26 is provided for simultaneously varying the energization of the mill motor is and the auxiliary or booster generator 22, whereby the speed of the reel to and work device l2 are simultaneously varied under all load conditions.

The speed of the mill motor It may be varied in any suitable manner as by changing the field excitation thereof through the use of the field energization controlling device 26, as is hereinafter more fully described. The roll'stand or work device I2 is adapted to have a strip of sheet or plate material I 3 pass therethrough in keeping with established practice. .The strip of material l3 after passing through or over various tensioning devices (not shown) is then wound upon the reel l0 which is driven by one or more of the motors l8 and 20 in order to provide a varying amount of capacity therefor, as is hereinafter described.

Both of the reel-motors l8 and 20 are connected in driving relation to the reel l0, and, in this instance, they are connected in tandem by means of a suitable coupling so that either one or both'of the motors may be used to drive the reel in. By driving the reel with both motors, the reel may be operated at low speeds under heavy load conditions.

Power is supplied to the mill and reel-motors, in this instance, by means of the main generator |6. An exciter generator 40 is utilized to supply excitation current to the field winding l5 of the mill motor, field windings l9 and 2| of the reel-motors and the field winding ll of the main generator [6. These generators, in addition to the auxiliary or booster generator 22, may be driven by a common motor 38, which receives its power from a suitable power supply (not shown).

The auxiliary or booster generator 22 may be connected in series with either one or both of the armatures of the reel-motors i8 and 20 to the main generator in order to vary the voltage of the motor armatures so as to regulate the speed of the reel [0, as hereinafter described. The auxiliary generator 22 is directly connected to the armature of motor la in series with the main power supply from generator l6 through conductor 46. The armatures of motors l8 and 2|) are also connected to the circuit controlling device 24 by conductors 41 and 48, respectively, with motor 20 being connected to the main bus 28 by conductor 49.

The controlling device 24, when in one position, as shown by the full lines in the drawing, connects the armatures of the reel-motors in series and to the power supply through

conductors

46, 41, 48 and 49. However, when the control device 24 is moved to its other position, as shown by dotted lines, the armature of motor l8 only is connected to the power supply, through

conductors

48, 41 and 50. Accordingly, it follows that an operator may selectively connect either one or both reel-motor armatures to the power supply conductors 28 and 30 in series with the auxiliary or booster generator 22.

However, it will be noted that, when changing the position of the circuit controlling device 24 to connect either one or both of the reel-motors to the power supply, the field connections of the auxiliary generator 22 are also changed so as to reverse the excitation of said generator. In addition, with the circuit controlling device 24 in its first position, with the reel-motor armatures in series, field resistor 32. is connected in series with the auxiliary generator field winding 23. With the control device 24 in its other (dotted) position, the resistor 33 is connected in series with the field winding 23, and the polarity of the field 23 is reversed. The polarity of the auxiliary generator field winding 23 is thus reversible so that this generator will boost or assist the voltage of the power supply when the two reelmotor armatures are in series and will buck or oppose the voltage of the power supply when only one motor is driving the reel, as is hereinafter more fully described.

'The excitation of the auxiliary generator 22 is varied simultaneously with the excitation of the mill motor 14, by means of an energization controlling device 26 so as to simultaneously vary the speed of the mill l2 and reel l0. The field energization controlling device 26 conrprises, in this instance, a manually operated elongated shaft 42 carrying a plurality of contactfingers 44a, 44b and 440. The

contacts

44a, 44b and 44c engage the

auxiliary field resistors

32 and 34, and the work device field resistor 36, respectively. The movable contact fingers are so positioned and connected with respect to their associated resistors that, as the device 26 is actuated to cause the contact finger 43c, engaging resistor 36, to increase the resistance in the circuit of the field winding E5 of the mill motor [4, the

resistor 32 is cut out or decreased while the resistor 34 is cut in or increased.

When utilizing the control system embodyin my invention, the armatures of the reel-motors I8 and 20 are connected in series by means of the circuit controlling device 24 when it is desired to increase the tension capacity of the reel beyond that which can be produced by one mo tor alone, even with the reel running at a low speed. When the armatures of the reel-motors l8 and 20 are connected in series, the resistor 32 is connected in series with the auxiliary generator field winding 23. This connection of the auxiliary generator field winding 23 is such as to cause the auxiliary generator 22 to boost the armature voltage applied to the reel-motors by the main generator l6. Accordingly, it follows that, when the field energization controlling de vice 26 is actuated so as to move the contact fingers to the left, resulting in a decreased field excitation. of the mill motor Ill so as to increase the speed of the mill, the contact finger controlling the excltation of the auxiliary generator 22 will likewise be moved to the left. This reduces the amount of resistance connected in series with the auxiliary generator field 23, thereby increasing the voltage applied to the reel-motors i8 and 20. The speed of the reel H] is thus simultaneously increased with that of the work In addition, it is apparent that, with the two reel-motors connected in tandem, the power developed thereby will be substantially twice that of a single motor. However, the inertia will be substantially reduced. Accordingly, the reel may be rotated at a slow speed with assurance that there is sufllcient torque to maintain the proper tension upon the strip material l3. It is to be understood that the speed variation of the reelmotors to take care of the reel build-up" is to be controlled by regulating the motor energization in any desired manner.

When it is desired to operate the mill at high speed under such conditions that the power output of a single motor would be sufiicient to operate the reel, the coupling 5| is disengaged so as to disconnect the reel-motor 20 from the motor i3 and reel ID. The circuit controlling device 24 is then changed to the dotted position as shown in the drawing, whereby the armature of reelmotor. 20 is disconnected from the main power supply. By changing the position of the circuit controlling device 24 the resistor 32 is disconnected from the auxiliary generator field 23 and resistor 34 is connected in series therewith. The polarity of said-field 23 is thus reversed, so that, in this instance, the auxiliary generator 22 will buck or oppose the voltage produced by the main generator I6. vHowever, with this setting the auxiliary generator may boost a small amount depending upon motor field resistor setting; for example, when said field is very weak and the mill is operating at top speed.

If it is desired to decrease the speed of operation of the mill by field control, with a single reelmotor connected for operation, the field energizetlon controlling device 26 is actuated so as to simultaneously move the contact fingers b and c to the right. The movable contact finger c thus reduces the amount of resistance connected in series with the mill motor field, increasing the energization thereof and reducing its speed. This movement of the contact finger 44b to the right reduces the resistance connected in series with the auxiliary generator field 23, so as to increase the excitation and voltage or said auxiliary generator. This increases the bucking action of the auxiliary generator 22 so as to reduce the voltage'applied to the armature of the reel-motor l8 and cause said motor to simultaneously reduce its speed with that of the mill motor.

Conversely, if it is desired to increase the speed of the reel l and work device I2, the contact fingers b and c are moved to the left. Accordingly, the excitation of the mill motor and the auxiliary booster are reduced. With a reduction in excitation of the auxiliary booster,' the voltage developed thereby is reduced. Accordingly, the bucking eilect is decreased so as to increase the voltage applied to the reel-motor 18.

It is to be understood that, by having the auxiliary or booster field, mill motor armature and reel-motor armatures all connected to the main generator, the entire mill may be stopped or started in unison. In addition, the speed of the mill may be varied by changing the voltage of the main generator in a well known manner.

It is, therefore, apparent that, with the control system embodying my invention, a plurality of driving motors may be connected in driving relation with a reel, either individually or in combination, so as to produce varying amounts of available torque or tension capacity while enabling the speed of the reel to be automatically regulated directly with that of the speed of the work device. In addition, it follows that, with such a control system, the reel-motor armatures may be selectively connected in series with an auxiliary generator whereby the power output of the auxiliary generator will simultaneously vary the speed of the reel with .01 the work device.

Various modifications may be made in the system embodying my invention without departing from the spirit and scope thereof, and I desire therefore that only such limitations shall be placed thereon as are imposed by the prior art and the appended claims.

I claim as my invention:

1. A motor control system comprising, a plurality oi electric motors, a source of power therefor, an auxiliary generator, circuit control means operable to connect one or all of the electric motors in series circuit relation with the auxiliary generator to the powersource, said circuit con trol means functioning to determine the polarity of the auxiliary generator whereby its voltage opposes the voltage of the power source when only 'one motor is connected thereto and assists the voltage of the power source when more than one motor is connected thereto, and means operable to vary the excitation of the auxiliary generator.

2. A motor control system comprising, a plurality'oi electric motors, a source of power therefor, an auxiliary generator having a field winding connected to the power source to cause said auxiliary generator to vary its voltage in accordance any changes in speed with any variation in the voltage of the powerv source, and switch means selectively operable to control the connections of the motors and field winding oi. the auxiliary generator to the power source whereby one 01' the motors may be connected in series circuit relation with the auxiliary generator to the power source with the polarity of the auxiliary generator in predetermined relation to that of the power source or all of the motors may be connected in series circuit relation with the auxiliary generator to the power source with the polarity of the auxiliary generator in another predetermined relation to that of the power source.

3. A motor control system comprising, a plurality of electric motors, an auxiliary generator having a field excitation winding, circuit control means operable to one position to connect one of the electric motors in series circuit relation with the auxiliary generator to a source of power and the field winding of the auxiliary generator to a source of excitation, said circuit control means being operable to another position to connect all of said electric motors in series circuit relation with the auxiliary generator to the power source and reverse the connection of the field winding of the auxiliary generator to the source of excitation, and means for varying the excitation current of the auxiliary generator when connected to the source of excitation in either direction.

4. A control system for rolling mill apparatus and the like having a work device operating on a strip of material and a winding reel for said strip comprising, a motor for driving said work device, a plurality of motors for driving said reel, an auxiliary generator, means connecting the armatures of the reel motors and auxiliary generator in series circuit relation with a source of power, means for varying the excitation of the auxiliary enerator, mean for varying the excitation of the motor driving the work device, and common actuating means for both of said resistance varying means for effecting simultaneous operation thereof.

5. A control system for rolling mill apparatus and the like having a work device operating on a strip of material and a winding reel for said strip comprising, a, motor for driving the work device, a plurality of motors for driving the reel, an auxiliaw generator, means connecting the armatures of the reel motors and the auxiliary generator in series circuit relation with a source of power, means for varying the excitation of the auxiliary generator, means for varying the excitation of the 'work device motor, and common actuating means for operating both of said excitation varying means simultaneously to increase the excitation of the auxiliary generator and decrease the excitation of the work device motor.

6. A control system for rolling mill apparatus and the like including a work deviceoperating on a strip of material, and a winding reel for said strip comprising, a motor for driving said work device, a plurality of motors for driving said reel, an auxiliary generator, a circuit controlling device movable between two positions, circuit means whereby the circuit controlling device in one position connects the armatures of the reel motors and auxiliary generator in series circuit relation with a source of power, other circuit means whereby the circuit controlling device in the second position connects the armature of one motor and the auxiliary generator in series circuit relation with the ource of power, and means including a pair or variable resistance devices and common actuating means therefor for simultaneously increasing the excitation of the auxiliary generator and reducing the excitation of the work device motor when said circuit controlling device is in said first position and for simultaneouslyoecreasing the excitation of the auxiliary genera tor and reducing the excitation of the work device motor when said circuit controlling device is in its said second position.

7. A control system for rolling mill apparatus and the like including a work device operating on a strip of material and a winding reel for said strip comprising, a motor for driving the work device, a plurality of motors for driving the reel, an auxiliary generator, a circuit controlling device operable between two positions, circuit means whereby the circuit controlling device in one position connects the armatures of more than one of the reel motors and the auxiliary generator in series circuit relation with a source-of power and connects the field winding-of the auxiliary generator to a source of excitation so that said generator will boost the voltage of the power source, and other circuit means whereby the circuit controlling device in the second position connects the armatures of only one reel motor and the auxiliary generator in series circuit relation with the source of power and reverses the connection of the field winding of the auxiliary generator to the excitation source so that said generator will buck the voltage of the power source.

8. A control system for rolling mill apparatus and the like including a work device for operating on a strip of material and a winding reel for said material comprising, a direct-current motor for driving the work device, a plurality of direct-current motors for driving the reel, an auxiliary generator, a circuit controlling device movable between two positions, circuit means whereby the circuit controlling device in one position connects the armatures of the reel motors and auxiliary generator in series circuit relation with a source of .power and connects the field winding of the auxiliary generator to a source of excitation so that said generator will develop a voltage to assist the voltage of the source of power, and other circuit means whereby the circuit controlling device in the second position connects the armatures of one reel motor and the auxiliary generator in series circuit relation with the source of power and reverses the connection of the field winding of the auxiliary generator to the excitation source so that said generator will develop a voltage to buck the voltage of the source of power, and means for F 5 simultaneously varying the excitation of the auxiliary generator and the work device motor in a predetermined manner, said means including current varying devices operable in unison by means of a common actuating device.

9. A- control system for rolling mill apparatus and the like including a work device for operating on a strip of material and a winding reel for the material comprising, a direct-current motor for driving the work device, a plurality of direct-current motors for driving the reel, an

auxiliary generator, a circuit controlling device movable between two positions, circuit means whereby the circuit controlling device in one :position connects the armatures of the reel motors and auxiliary generator in series circuit relation with a source of power and connects the auxiliary generator field winding to a source of excitation so that said generator will develop a voltage to assist the voltage of the source of power, and other circuit means whereby the circuit controlling device in the second position connects the armatures of one reel motor and the auxiliary generator in series circuit relation with the source of power and reverses the connection of the auxiliary generator field winding so that said generator will develop a voltage to buck the voltage of the source of power, and means for simultaneously increasing the excitation of the auxiliary generator and reducing the excitation of the work device motor when said circuit controlling device is in its said first position and for simultaneously decreasing the excitation of the auxiliary generator and reducing the excitation of the work device motor when said circuit controlling device is in its said second position, whereby the rotative speed of reel will increase in proportion to the increase of speed of the work device, said means including a variable resistor connected in the field excitation circuit of the work device motor and a pair of variable resistors each of which is included in one of the two different field excitation circuits of the auxiliary generator as determined by the position of the circuit controlling device and a common actuating means for said variable resistors.

WILLARD G. COOK.